A shift register may operate as a gate driving circuit of a display device to sequentially supply a gate scan signal to the gate lines to turn on the transistors in the rows of pixels, thus allowing writing of data signals into the pixels.
In order to fully turn on the transistors, the high level of the gate scan signal typically needs to reach 25 V or more. Due to the self-boosting effect of the storage capacitor in the shift register, the voltage at some internal nodes of the shift register may even be higher, for example, more than a factor of two above the high level of the gate-scan signal (above 50 V). Such a high voltage causes a large change in the characteristics of the transistors connected to these internal nodes, resulting in a threshold voltage drift. If the display device operates under such a condition for a long time, the shift register may become unstable, leading to a degraded gate scanning signal.